In general, devices are known that diffuse a flow of warm air, e.g. in the cockpit of a rotorcraft, both under the seats of the occupants (heater function), and over the windshield (demisting function).
A first known device comprises an electric fan serving to cause cold ambient air to circulate along a heater and/or demister circuit. A flow of hot air, made up of a compressed gas picked up from the outlet of the compressor of the rotorcraft engine, is propelled into this heater and/or demister circuit via an injector. Under such conditions, on mixing, the flow of ambient air and the flow of hot air create a flow of warm air which is subsequently delivered to the cockpit of the rotorcraft. The pilot can adjust the temperature of the flow of warm air by reducing or increasing the flow rate of the hot air.
That first device is effective, but it presents the drawback of being very noisy, where the noise is the result of the hot air flow being ejected, and can be as high as one hundred decibels.
A second known device operates on the same principle but does not make use of an electric fan. The flow of hot air is accelerated by an injector which opens out into the throat of a venturi, thereby creating suction that sucks in cold air from the surroundings.
That second device has the advantage of not consuming electricity, but it remains extremely noisy insofar as the flow of hot air continues to be ejected in the same manner. Hearing the noise continuously quickly makes perception of the noise intolerable.